1. Field of the Invention
The present invention relates to techniques for generating clock signals. In particular, the present invention relates to techniques for generating non-overlapping clocks.
2. Description of the Prior Art
Most integrated receivers used on cellular products today have to be able to achieve high levels of sensitivity in the presence of large close in and out of band blockers. This has historically required the use of high Q narrow band filters. The requirement has typically been met with a combination of surface acoustic wave (SAW) filters and high Q on-chip inductors to narrow band the receive chain. The disadvantage of a narrow band receive chain is that multiple front ends, which include the low noise amplifier (LNA), may be necessary to cover multiple cellular bands.
A translational filter capable of translating a low frequency response to higher frequencies can be used in receivers having to cover multiple cellular bands. The characteristics of a translational filter are defined in terms of in-band gain, Q and out-of-band rejection. A study has shown that these important characteristics are highly dependent on the duty cycle and non-overlapping characteristics of signals provided by the local oscillator (LO) for tuning the translational filter. Furthermore, it has been demonstrated that the translational filter has little to no effect on reciprocal mixing and as such the LO must have low phase noise at the reciprocal mixing offset frequencies.